August 1-7, 2006
Midwest Weekly Highlights - August 1-7, 2006
Heat Wave Extends Into Early
August
The heat wave that ended July
ushered in the first few
days of August. A weak cold front pushed through the Midwest
near the middle of the first week, bringing some relief from the heat
and humidity. Temperatures for the first week of August (Figure 1)
ranged
from 8°F above normal in southwestern Missouri to near to slightly
below normal in northwestern Minnesota. However, much of the
southeastern two-thirds of the region experienced temperatures ranging
from 5°F to 7°F above normal. The cooler temperatures in
the northwestern third of the region were reflective of the passage of
the cold front at the beginning of the week.
Rainfall this week was concentrated in a band from northwestern Iowa
across southern Minnesota and into the northern half of Wisconsin
(Figure 2). This was where the cold front stalled out on
the
first two days of the month before resuming its southward march.
Rainfall in this area ranged from as much as three to five
inches, two to five times normal for the week. This area has
been
in an intensifying drought for the last several months (Figure 3),
and
the rain was badly needed. The drought has reached the Extreme category
in western and northwestern Minnesota.
Rainfall since May 1 has been 50 to 75
percent of normal in the western portions of the region which has been
dominated by the upper level ridge for most of the summer (Figure 4).
Rainfall has been at or above normal in the eastern Ohio Valley
and in the northeastern quarter of the region.
Records
Tumble First Three Days
On August 1 the leading edge of cooler and drier air was beginning to
push into northern Minnesota (Figure 5),
but the rest of the region
continued to bake under the ridge of high pressure aloft.
While
temperatures reached only the mid 70s in central Minnesota, much of
Missouri reached triple digits and upper 90s were observed as far north
as Alpena, MI (Figure 6)
While a number of locations set new
record high temperatures, the most notable and numerous records were
record high minimum temperatures. Very humid air, marked by dewpoints
in the mid and upper 70s, trapped the heat preventing
significant nighttime cooling. A failed substation caused a
power
blackout on the south side of Chicago on the evening on July
31
which continued well into Tuesday, August 1. As temperature rose into
the low 90s by late morning, Chicago officials evacuated more than
1,000 residents from high-rises in the densely populated area taking
some to hotels and the majority to the McCormick Place Convention
Center. Power failed on the northwest side of Chicago on the evening of
August 1, leaving 2,600 customers without power. Other scattered power
outages also occurred. Officials reported that 41 people were
transported to hospitals with heat-related illness, and one fatality
was attributed to heat-related causes in Chicago. An 80
year-old
man in Edwardsville, IL (Madison County)
was also suspected to have died due to the heat. The table below
contains some of the records established the first three days of the
month.
Stalled
Front Focuses Rain in Parts of Drought-Stricken Area
A cold front pushing into the northern Midwest stalled
across northwestern Iowa, southern Minnesota, and northwestern
Wisconsin on August 1. Thunderstorms erupted along the front and moved
northeastward on August 1-2, depositing up to six inches of rain in
northern Iowa and three to four inches of rain in southern Minnesota (Figure 7).
Minneapolis-St.Paul received 2.69 inches of rain on August 2, setting a
new daily rainfall record (the old record was 2.39 inches in 1956).
Over the course of the two days two to four inches of rain accumulated
from northwestern Iowa to northwestern Wisconsin. Some of the
more significant amounts include: 5.95", Titonka, IA;
5.47", Estherville, IA; 5.38", Ringsted, IA; 4.58", Lake
Mills, IA; 4.06", Spirit Lake, IA; 5.58", Fairmont, MN;
5.11", St. Paul, MN (University of Minnesota); 4.05", Owen,
WI.
Tornadoes and Severe Weather
The storms responsible for the heavy rain in the
upper Midwest also
produced severe weather, with high winds the most common report.
Two tornadoes touched down in Watonwan County, MN on the
night of
August 1. The
Twin Cities, MN National Weather Service office investigation found that the first tornado caused damage rated as F3, completely
destroying one farmstead. A second tornado, rated an F1,
causing building damage along its path. Fortunately, there were no
injuries reported from either of the tornadoes.
Severe thunderstorms continued along the front in Iowa, Illinois, and
Michigan on August 2 as the front crept to the southeast. On August 3
the focus of the severe weather was in Ohio, where one tornado touched
down near Mt. Vernon (Knox County), causing one injury, destroying a lumber yard
building and damaging 15 vehicles.
Severe
thunderstorms broke out across northwestern Minnesota on August 5 as
another front pushed in from the Northern Plains.
Eyewitnesses reported at least three and possibly four
distinct tornadoes touching down in Roseau and Lake of the Wood Counties, MN. One tornado
touched down in Warroad, MN, quickly intensifying and reaching
a width of 500 yards. This tornado caused F3 damage to a window factory
complex in the northwest portion of Warroad. Softball-size
hail was also reported with this storm.
Heat Breaks for Most
Cool high pressure brought relief from the heat
and humidity to much of the Midwest on August 5-7, with temperatures
returning to near normal levels except for the far southern and
southwestern edges of the region. Record high temperatures
for August 7 were reported in Jackson, KY (92°F, tying record set in
1999 and London, KY (95°F, old record 93°F in 1980). A record high
minimum temperature was set in in Louisville, KY (78°F, old record 77°F
in 1916).
SDH